A Short History of Nearly Everything

To Meghan and Chris. Welcome.





The physicist Leo Szilard once announced to his friend Hans Bethe that he was thinking of keeping a diary: “I don’t intend to publish. I am merely going to record the facts for the information of God.” “Don’t you think God knows the facts?” Bethe asked. “Yes,” said Szilard. “He knows the facts, but He does not know this version of the facts.”

—Hans Christian von Baeyer, Taming the Atom

Acknowledgments


As I sit here, in early 2003, I have before me several pages of manuscript bearing majestically encouraging and tactful notes from Ian Tattersall of the American Museum of Natural History pointing out, inter alia, that Périgueux is not a wine-producing region, that it is inventive but a touch unorthodox of me to italicize taxonomic divisions above the level of genus and species, that I have persistently misspelled Olorgesaille (a place that I only recently visited), and so on in similar vein through two chapters of text covering his area of expertise, early humans.

Goodness knows how many other inky embarrassments may lurk in these pages yet, but it is thanks to Dr. Tattersall and all of those whom I am about to mention that there aren’t many hundreds more. I cannot begin to thank adequately those who helped me in the preparation of this book. I am especially indebted to the following, who were uniformly generous and kindly and showed the most heroic reserves of patience in answering one simple, endlessly repeated question: “I’m sorry, but can you explain that again?”

In the United States: Ian Tattersall of the American Museum of Natural History in New York; John Thorstensen, Mary K. Hudson, and David Blanchflower of Dartmouth College in Hanover, New Hampshire; Dr. William Abdu and Dr. Bryan Marsh of Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire; Ray Anderson and Brian Witzke of the Iowa Department of Natural Resources, Iowa City; Mike Voorhies of the University of Nebraska and Ashfall Fossil Beds State Park near Orchard, Nebraska; Chuck Offenburger of Buena Vista University, Storm Lake, Iowa; Ken Rancourt, director of research, Mount Washington Observatory, Gorham, New Hampshire; Paul Doss, geologist of Yellowstone National Park, and his wife, Heidi, also of the National Park; Frank Asaro of the University of California at Berkeley; Oliver Payne and Lynn Addison of the National Geographic Society; James O. Farlow, Indiana-Purdue University; Roger L. Larson, professor of marine geophysics, University of Rhode Island; Jeff Guinn of the Fort Worth Star-Telegram newspaper; Jerry Kasten of Dallas, Texas; and the staff of the Iowa Historical Society in Des Moines.

In England: David Caplin of Imperial College, London; Richard Fortey, Len Ellis, and Kathy Way of the Natural History Museum; Martin Raff of University College, London; Rosalind Harding of the Institute of Biological Anthropology in Oxford; Dr. Laurence Smaje, formerly of the Wellcome Institute; and Keith Blackmore of The Times.

In Australia: the Reverend Robert Evans of Hazelbrook, New South Wales; Alan Thorne and Victoria Bennett of the Australian National University in Canberra; Louise Burke and John Hawley of Canberra; Anne Milne of the Sydney Morning Herald; Ian Nowak, formerly of the Geological Society of Western Australia; Thomas H. Rich of Museum Victoria; Tim Flannery, director of the South Australian Museum in Adelaide; and the very helpful staff of the State Library of New South Wales in Sydney.

And elsewhere: Sue Superville, information center manager at the Museum of New Zealand in Wellington, and Dr. Emma Mbua, Dr. Koen Maes, and Jillani Ngalla of the Kenya National Museum in Nairobi.

I am also deeply and variously indebted to Patrick Janson-Smith, Gerald Howard, Marianne Velmans, Alison Tulett, Larry Finlay, Steve Rubin, Jed Mattes, Carol Heaton, Charles Elliott, David Bryson, Felicity Bryson, Dan McLean, Nick Southern, Patrick Gallagher, Larry Ashmead, and the staff of the peerless and ever-cheery Howe Library in Hanover, New Hampshire.

Above all, and as always, my profoundest thanks to my dear, patient, incomparable wife, Cynthia.

Introduction

Welcome. And congratulations. I am delighted that you could make it. Getting here wasn’t easy, I know. In fact, I suspect it was a little tougher than you realize.

To begin with, for you to be here now trillions of drifting atoms had somehow to assemble in an intricate and intriguingly obliging manner to create you. It’s an arrangement so specialized and particular that it has never been tried before and will only exist this once. For the next many years (we hope) these tiny particles will uncomplainingly engage in all the billions of deft, cooperative efforts necessary to keep you intact and let you experience the supremely agreeable but generally underappreciated state known as existence.

Why atoms take this trouble is a bit of a puzzle. Being you is not a gratifying experience at the atomic level. For all their devoted attention, your atoms don’t actually care about you—indeed, don’t even know that you are there. They don’t even know that they are there. They are mindless particles, after all, and not even themselves alive. (It is a slightly arresting notion that if you were to pick yourself apart with tweezers, one atom at a time, you would produce a mound of fine atomic dust, none of which had ever been alive but all of which had once been you.) Yet somehow for the period of your existence they will answer to a single overarching impulse: to keep you you.

The bad news is that atoms are fickle and their time of devotion is fleeting—fleeting indeed. Even a long human life adds up to only about 650,000 hours. And when that modest milestone flashes past, or at some other point thereabouts, for reasons unknown your atoms will shut you down, silently disassemble, and go off to be other things. And that’s it for you.

Still, you may rejoice that it happens at all. Generally speaking in the universe it doesn’t, so far as we can tell. This is decidedly odd because the atoms that so liberally and congenially flock together to form living things on Earth are exactly the same atoms that decline to do it elsewhere. Whatever else it may be, at the level of chemistry life is curiously mundane: carbon, hydrogen, oxygen, and nitrogen, a little calcium, a dash of sulfur, a light dusting of other very ordinary elements—nothing you wouldn’t find in any ordinary drugstore—and that’s all you need. The only thing special about the atoms that make you is that they make you. That is of course the miracle of life.

Whether or not atoms make life in other corners of the universe, they make plenty else; indeed, they make everything else. Without them there would be no water or air or rocks, no stars and planets, no distant gassy clouds or swirling nebulae or any of the other things that make the universe so usefully material. Atoms are so numerous and necessary that we easily overlook that they needn’t actually exist at all. There is no law that requires the universe to fill itself with small particles of matter or to produce light and gravity and the other physical properties on which our existence hinges. There needn’t actually be a universe at all. For the longest time there wasn’t. There were no atoms and no universe for them to float about in. There was nothing—nothing at all anywhere.

So thank goodness for atoms. But the fact that you have atoms and that they assemble in such a willing manner is only part of what got you here. To be here now, alive in the twenty-first century and smart enough to know it, you also had to be the beneficiary of an extraordinary string of biological good fortune. Survival on Earth is a surprisingly tricky business. Of the billions and billions of species of living thing that have existed since the dawn of time, most—99.99 percent—are no longer around. Life on Earth, you see, is not only brief but dismayingly tenuous. It is a curious feature of our existence that we come from a planet that is very good at promoting life but even better at extinguishing it.

The average species on Earth lasts for only about four million years, so if you wish to be around for billions of years, you must be as fickle as the atoms that made you. You must be prepared to change everything about yourself—shape, size, color, species affiliation, everything—and to do so repeatedly. That’s much easier said than done, because the process of change is random. To get from “protoplasmal primordial atomic globule” (as the Gilbert and Sullivan song put it) to sentient upright modern human has required you to mutate new traits over and over in a precisely timely manner for an exceedingly long while. So at various periods over the last 3.8 billion years you have abhorred oxygen and then doted on it, grown fins and limbs and jaunty sails, laid eggs, flicked the air with a forked tongue, been sleek, been furry, lived underground, lived in trees, been as big as a deer and as small as a mouse, and a million things more. The tiniest deviation from any of these evolutionary shifts, and you might now be licking algae from cave walls or lolling walruslike on some stony shore or disgorging air through a blowhole in the top of your head before diving sixty feet for a mouthful of delicious sandworms.

Not only have you been lucky enough to be attached since time immemorial to a favored evolutionary line, but you have also been extremely—make that miraculously—fortunate in your personal ancestry. Consider the fact that for 3.8 billion years, a period of time older than the Earth’s mountains and rivers and oceans, every one of your forebears on both sides has been attractive enough to find a mate, healthy enough to reproduce, and sufficiently blessed by fate and circumstances to live long enough to do so. Not one of your pertinent ancestors was squashed, devoured, drowned, starved, stranded, stuck fast, untimely wounded, or otherwise deflected from its life’s quest of delivering a tiny charge of genetic material to the right partner at the right moment in order to perpetuate the only possible sequence of hereditary combinations that could result—eventually, astoundingly, and all too briefly—in you.

 

This is a book about how it happened—in particular how we went from there being nothing at all to there being something, and then how a little of that something turned into us, and also some of what happened in between and since. That’s a great deal to cover, of course, which is why the book is called A Short History of Nearly Everything, even though it isn’t really. It couldn’t be. But with luck by the time we finish it will feel as if it is.

My own starting point, for what it’s worth, was an illustrated science book that I had as a classroom text when I was in fourth or fifth grade. The book was a standard-issue 1950s schoolbook—battered, unloved, grimly hefty—but near the front it had an illustration that just captivated me: a cutaway diagram showing the Earth’s interior as it would look if you cut into the planet with a large knife and carefully withdrew a wedge representing about a quarter of its bulk.

It’s hard to believe that there was ever a time when I had not seen such an illustration before, but evidently I had not for I clearly remember being transfixed. I suspect, in honesty, my initial interest was based on a private image of streams of unsuspecting eastbound motorists in the American plains states plunging over the edge of a sudden 4,000-mile-high cliff running between Central America and the North Pole, but gradually my attention did turn in a more scholarly manner to the scientific import of the drawing and the realization that the Earth consisted of discrete layers, ending in the center with a glowing sphere of iron and nickel, which was as hot as the surface of the Sun, according to the caption, and I remember thinking with real wonder: “How do they know that?”

I didn’t doubt the correctness of the information for an instant—I still tend to trust the pronouncements of scientists in the way I trust those of surgeons, plumbers, and other possessors of arcane and privileged information—but I couldn’t for the life of me conceive how any human mind could work out what spaces thousands of miles below us, that no eye had ever seen and no X ray could penetrate, could look like and be made of. To me that was just a miracle. That has been my position with science ever since.

Excited, I took the book home that night and opened it before dinner—an action that I expect prompted my mother to feel my forehead and ask if I was all right—and, starting with the first page, I read.

And here’s the thing. It wasn’t exciting at all. It wasn’t actually altogether comprehensible. Above all, it didn’t answer any of the questions that the illustration stirred up in a normal inquiring mind: How did we end up with a Sun in the middle of our planet? And if it is burning away down there, why isn’t the ground under our feet hot to the touch? And why isn’t the rest of the interior melting—or is it? And when the core at last burns itself out, will some of the Earth slump into the void, leaving a giant sinkhole on the surface? And how do you know this? How did you figure it out?

But the author was strangely silent on such details—indeed, silent on everything but anticlines, synclines, axial faults, and the like. It was as if he wanted to keep the good stuff secret by making all of it soberly unfathomable. As the years passed, I began to suspect that this was not altogether a private impulse. There seemed to be a mystifying universal conspiracy among textbook authors to make certain the material they dealt with never strayed too near the realm of the mildly interesting and was always at least a long-distance phone call from the frankly interesting.

I now know that there is a happy abundance of science writers who pen the most lucid and thrilling prose—Timothy Ferris, Richard Fortey, and Tim Flannery are three that jump out from a single station of the alphabet (and that’s not even to mention the late but godlike Richard Feynman)—but sadly none of them wrote any textbook I ever used. All mine were written by men (it was always men) who held the interesting notion that everything became clear when expressed as a formula and the amusingly deluded belief that the children of America would appreciate having chapters end with a section of questions they could mull over in their own time. So I grew up convinced that science was supremely dull, but suspecting that it needn’t be, and not really thinking about it at all if I could help it. This, too, became my position for a long time.

Then much later—about four or five years ago—I was on a long flight across the Pacific, staring idly out the window at moonlit ocean, when it occurred to me with a certain uncomfortable forcefulness that I didn’t know the first thing about the only planet I was ever going to live on. I had no idea, for example, why the oceans were salty but the Great Lakes weren’t. Didn’t have the faintest idea. I didn’t know if the oceans were growing more salty with time or less, and whether ocean salinity levels was something I should be concerned about or not. (I am very pleased to tell you that until the late 1970s scientists didn’t know the answers to these questions either. They just didn’t talk about it very audibly.)

And ocean salinity of course represented only the merest sliver of my ignorance. I didn’t know what a proton was, or a protein, didn’t know a quark from a quasar, didn’t understand how geologists could look at a layer of rock on a canyon wall and tell you how old it was, didn’t know anything really. I became gripped by a quiet, unwonted urge to know a little about these matters and to understand how people figured them out. That to me remained the greatest of all amazements—how scientists work things out. How does anybody know how much the Earth weighs or how old its rocks are or what really is way down there in the center? How can they know how and when the universe started and what it was like when it did? How do they know what goes on inside an atom? And how, come to that—or perhaps above all—can scientists so often seem to know nearly everything but then still can’t predict an earthquake or even tell us whether we should take an umbrella with us to the races next Wednesday?

So I decided that I would devote a portion of my life—three years, as it now turns out—to reading books and journals and finding saintly, patient experts prepared to answer a lot of outstandingly dumb questions. The idea was to see if it isn’t possible to understand and appreciate—marvel at, enjoy even—the wonder and accomplishments of science at a level that isn’t too technical or demanding, but isn’t entirely superficial either.

That was my idea and my hope, and that is what the book that follows is intended to be. Anyway, we have a great deal of ground to cover and much less than 650,000 hours in which to do it, so let’s begin.

1 How to build a Universe

NO MATTER HOW hard you try you will never be able to grasp just how tiny, how spatially unassuming, is a proton. It is just way too small.

A proton is an infinitesimal part of an atom, which is itself of course an insubstantial thing. Protons are so small that a little dib of ink like the dot on this i can hold something in the region of 500,000,000,000 of them, rather more than the number of seconds contained in half a million years. So protons are exceedingly microscopic, to say the very least.

Now imagine if you can (and of course you can’t) shrinking one of those protons down to a billionth of its normal size into a space so small that it would make a proton look enormous. Now pack into that tiny, tiny space about an ounce of matter. Excellent. You are ready to start a universe.

I’m assuming of course that you wish to build an inflationary universe. If you’d prefer instead to build a more old-fashioned, standard Big Bang universe, you’ll need additional materials. In fact, you will need to gather up everything there is—every last mote and particle of matter between here and the edge of creation—and squeeze it into a spot so infinitesimally compact that it has no dimensions at all. It is known as a singularity.

In either case, get ready for a really big bang. Naturally, you will wish to retire to a safe place to observe the spectacle. Unfortunately, there is nowhere to retire to because outside the singularity there is no where. When the universe begins to expand, it won’t be spreading out to fill a larger emptiness. The only space that exists is the space it creates as it goes.

It is natural but wrong to visualize the singularity as a kind of pregnant dot hanging in a dark, boundless void. But there is no space, no darkness. The singularity has no “around” around it. There is no space for it to occupy, no place for it to be. We can’t even ask how long it has been there—whether it has just lately popped into being, like a good idea, or whether it has been there forever, quietly awaiting the right moment. Time doesn’t exist. There is no past for it to emerge from.

And so, from nothing, our universe begins.

In a single blinding pulse, a moment of glory much too swift and expansive for any form of words, the singularity assumes heavenly dimensions, space beyond conception. In the first lively second (a second that many cosmologists will devote careers to shaving into ever-finer wafers) is produced gravity and the other forces that govern physics. In less than a minute the universe is a million billion miles across and growing fast. There is a lot of heat now, ten billion degrees of it, enough to begin the nuclear reactions that create the lighter elements—principally hydrogen and helium, with a dash (about one atom in a hundred million) of lithium. In three minutes, 98 percent of all the matter there is or will ever be has been produced. We have a universe. It is a place of the most wondrous and gratifying possibility, and beautiful, too. And it was all done in about the time it takes to make a sandwich.

When this moment happened is a matter of some debate. Cosmologists have long argued over whether the moment of creation was 10 billion years ago or twice that or something in between. The consensus seems to be heading for a figure of about 13.7 billion years, but these things are notoriously difficult to measure, as we shall see further on. All that can really be said is that at some indeterminate point in the very distant past, for reasons unknown, there came the moment known to science as t = 0. We were on our way.

There is of course a great deal we don’t know, and much of what we think we know we haven’t known, or thought we’ve known, for long. Even the notion of the Big Bang is quite a recent one. The idea had been kicking around since the 1920s, when Georges Lemaître, a Belgian priest-scholar, first tentatively proposed it, but it didn’t really become an active notion in cosmology until the mid-1960s when two young radio astronomers made an extraordinary and inadvertent discovery.

Their names were Arno Penzias and Robert Wilson. In 1965, they were trying to make use of a large communications antenna owned by Bell Laboratories at Holmdel, New Jersey, but they were troubled by a persistent background noise—a steady, steamy hiss that made any experimental work impossible. The noise was unrelenting and unfocused. It came from every point in the sky, day and night, through every season. For a year the young astronomers did everything they could think of to track down and eliminate the noise. They tested every electrical system. They rebuilt instruments, checked circuits, wiggled wires, dusted plugs. They climbed into the dish and placed duct tape over every seam and rivet. They climbed back into the dish with brooms and scrubbing brushes and carefully swept it clean of what they referred to in a later paper as “white dielectric material,” or what is known more commonly as bird shit. Nothing they tried worked.

Unknown to them, just thirty miles away at Princeton University, a team of scientists led by Robert Dicke was working on how to find the very thing they were trying so diligently to get rid of. The Princeton researchers were pursuing an idea that had been suggested in the 1940s by the Russian-born astrophysicist George Gamow that if you looked deep enough into space you should find some cosmic background radiation left over from the Big Bang. Gamow calculated that by the time it crossed the vastness of the cosmos, the radiation would reach Earth in the form of microwaves. In a more recent paper he had even suggested an instrument that might do the job: the Bell antenna at Holmdel. Unfortunately, neither Penzias and Wilson, nor any of the Princeton team, had read Gamow’s paper.

The noise that Penzias and Wilson were hearing was, of course, the noise that Gamow had postulated. They had found the edge of the universe, or at least the visible part of it, 90 billion trillion miles away. They were “seeing” the first photons—the most ancient light in the universe—though time and distance had converted them to microwaves, just as Gamow had predicted. In his book The Inflationary Universe, Alan Guth provides an analogy that helps to put this finding in perspective. If you think of peering into the depths of the universe as like looking down from the hundredth floor of the Empire State Building (with the hundredth floor representing now and street level representing the moment of the Big Bang), at the time of Wilson and Penzias’s discovery the most distant galaxies anyone had ever detected were on about the sixtieth floor, and the most distant things—quasars—were on about the twentieth. Penzias and Wilson’s finding pushed our acquaintance with the visible universe to within half an inch of the sidewalk.

Still unaware of what caused the noise, Wilson and Penzias phoned Dicke at Princeton and described their problem to him in the hope that he might suggest a solution. Dicke realized at once what the two young men had found. “Well, boys, we’ve just been scooped,” he told his colleagues as he hung up the phone.

Soon afterward the Astrophysical Journal published two articles: one by Penzias and Wilson describing their experience with the hiss, the other by Dicke’s team explaining its nature. Although Penzias and Wilson had not been looking for cosmic background radiation, didn’t know what it was when they had found it, and hadn’t described or interpreted its character in any paper, they received the 1978 Nobel Prize in physics. The Princeton researchers got only sympathy. According to Dennis Overbye in Lonely Hearts of the Cosmos, neither Penzias nor Wilson altogether understood the significance of what they had found until they read about it in the New York Times.

Incidentally, disturbance from cosmic background radiation is something we have all experienced. Tune your television to any channel it doesn’t receive, and about 1 percent of the dancing static you see is accounted for by this ancient remnant of the Big Bang. The next time you complain that there is nothing on, remember that you can always watch the birth of the universe.

 

Although everyone calls it the Big Bang, many books caution us not to think of it as an explosion in the conventional sense. It was, rather, a vast, sudden expansion on a whopping scale. So what caused it?

One notion is that perhaps the singularity was the relic of an earlier, collapsed universe—that we’re just one of an eternal cycle of expanding and collapsing universes, like the bladder on an oxygen machine. Others attribute the Big Bang to what they call “a false vacuum” or “a scalar field” or “vacuum energy”—some quality or thing, at any rate, that introduced a measure of instability into the nothingness that was. It seems impossible that you could get something from nothing, but the fact that once there was nothing and now there is a universe is evident proof that you can. It may be that our universe is merely part of many larger universes, some in different dimensions, and that Big Bangs are going on all the time all over the place. Or it may be that space and time had some other forms altogether before the Big Bang—forms too alien for us to imagine—and that the Big Bang represents some sort of transition phase, where the universe went from a form we can’t understand to one we almost can. “These are very close to religious questions,” Dr. Andrei Linde, a cosmologist at Stanford, told the New York Times in 2001.

The Big Bang theory isn’t about the bang itself but about what happened after the bang. Not long after, mind you. By doing a lot of math and watching carefully what goes on in particle accelerators, scientists believe they can look back to 10-43 seconds after the moment of creation, when the universe was still so small that you would have needed a microscope to find it. We mustn’t swoon over every extraordinary number that comes before us, but it is perhaps worth latching on to one from time to time just to be reminded of their ungraspable and amazing breadth. Thus 10-43 is 0.000000000000000000000 0000000000000000000001, or one 10 million trillion trillion trillionths of a second.*1

Most of what we know, or believe we know, about the early moments of the universe is thanks to an idea called inflation theory first propounded in 1979 by a junior particle physicist, then at Stanford, now at MIT, named Alan Guth. He was thirty-two years old and, by his own admission, had never done anything much before. He would probably never have had his great theory except that he happened to attend a lecture on the Big Bang given by none other than Robert Dicke. The lecture inspired Guth to take an interest in cosmology, and in particular in the birth of the universe.

The eventual result was the inflation theory, which holds that a fraction of a moment after the dawn of creation, the universe underwent a sudden dramatic expansion. It inflated—in effect ran away with itself, doubling in size every 10-34 seconds. The whole episode may have lasted no more than 10-30 seconds—that’s one million million million million millionths of a second—but it changed the universe from something you could hold in your hand to something at least 10,000,000,000,000,000,000,000,000 times bigger. Inflation theory explains the ripples and eddies that make our universe possible. Without it, there would be no clumps of matter and thus no stars, just drifting gas and everlasting darkness.

According to Guth’s theory, at one ten-millionth of a trillionth of a trillionth of a trillionth of a second, gravity emerged. After another ludicrously brief interval it was joined by electromagnetism and the strong and weak nuclear forces—the stuff of physics. These were joined an instant later by swarms of elementary particles—the stuff of stuff. From nothing at all, suddenly there were swarms of photons, protons, electrons, neutrons, and much else—between 1079 and 1089 of each, according to the standard Big Bang theory.

Such quantities are of course ungraspable. It is enough to know that in a single cracking instant we were endowed with a universe that was vast—at least a hundred billion light-years across, according to the theory, but possibly any size up to infinite—and perfectly arrayed for the creation of stars, galaxies, and other complex systems.

What is extraordinary from our point of view is how well it turned out for us. If the universe had formed just a tiny bit differently—if gravity were fractionally stronger or weaker, if the expansion had proceeded just a little more slowly or swiftly—then there might never have been stable elements to make you and me and the ground we stand on. Had gravity been a trifle stronger, the universe itself might have collapsed like a badly erected tent, without precisely the right values to give it the right dimensions and density and component parts. Had it been weaker, however, nothing would have coalesced. The universe would have remained forever a dull, scattered void.

This is one reason that some experts believe there may have been many other big bangs, perhaps trillions and trillions of them, spread through the mighty span of eternity, and that the reason we exist in this particular one is that this is one we could exist in. As Edward P. Tryon of Columbia University once put it: “In answer to the question of why it happened, I offer the modest proposal that our Universe is simply one of those things which happen from time to time.” To which adds Guth: “Although the creation of a universe might be very unlikely, Tryon emphasized that no one had counted the failed attempts.”

Martin Rees, Britain’s astronomer royal, believes that there are many universes, possibly an infinite number, each with different attributes, in different combinations, and that we simply live in one that combines things in the way that allows us to exist. He makes an analogy with a very large clothing store: “If there is a large stock of clothing, you’re not surprised to find a suit that fits. If there are many universes, each governed by a differing set of numbers, there will be one where there is a particular set of numbers suitable to life. We are in that one.”

Rees maintains that six numbers in particular govern our universe, and that if any of these values were changed even very slightly things could not be as they are. For example, for the universe to exist as it does requires that hydrogen be converted to helium in a precise but comparatively stately manner—specifically, in a way that converts seven one-thousandths of its mass to energy. Lower that value very slightly—from 0.007 percent to 0.006 percent, say—and no transformation could take place: the universe would consist of hydrogen and nothing else. Raise the value very slightly—to 0.008 percent—and bonding would be so wildly prolific that the hydrogen would long since have been exhausted. In either case, with the slightest tweaking of the numbers the universe as we know and need it would not be here.

I should say that everything is just right so far. In the long term, gravity may turn out to be a little too strong, and one day it may halt the expansion of the universe and bring it collapsing in upon itself, till it crushes itself down into another singularity, possibly to start the whole process over again. On the other hand it may be too weak and the universe will keep racing away forever until everything is so far apart that there is no chance of material interactions, so that the universe becomes a place that is inert and dead, but very roomy. The third option is that gravity is just right—“critical density” is the cosmologists’ term for it—and that it will hold the universe together at just the right dimensions to allow things to go on indefinitely. Cosmologists in their lighter moments sometimes call this the Goldilocks effect—that everything is just right. (For the record, these three possible universes are known respectively as closed, open, and flat.)

Now the question that has occurred to all of us at some point is: what would happen if you traveled out to the edge of the universe and, as it were, put your head through the curtains? Where would your head be if it were no longer in the universe? What would you find beyond? The answer, disappointingly, is that you can never get to the edge of the universe. That’s not because it would take too long to get there—though of course it would—but because even if you traveled outward and outward in a straight line, indefinitely and pugnaciously, you would never arrive at an outer boundary. Instead, you would come back to where you began (at which point, presumably, you would rather lose heart in the exercise and give up). The reason for this is that the universe bends, in a way we can’t adequately imagine, in conformance with Einstein’s theory of relativity (which we will get to in due course). For the moment it is enough to know that we are not adrift in some large, ever-expanding bubble. Rather, space curves, in a way that allows it to be boundless but finite. Space cannot even properly be said to be expanding because, as the physicist and Nobel laureate Steven Weinberg notes, “solar systems and galaxies are not expanding, and space itself is not expanding.” Rather, the galaxies are rushing apart. It is all something of a challenge to intuition. Or as the biologist J. B. S. Haldane once famously observed: “The universe is not only queerer than we suppose; it is queerer than we can suppose.”

The analogy that is usually given for explaining the curvature of space is to try to imagine someone from a universe of flat surfaces, who had never seen a sphere, being brought to Earth. No matter how far he roamed across the planet’s surface, he would never find an edge. He might eventually return to the spot where he had started, and would of course be utterly confounded to explain how that had happened. Well, we are in the same position in space as our puzzled flatlander, only we are flummoxed by a higher dimension.

Just as there is no place where you can find the edge of the universe, so there is no place where you can stand at the center and say: “This is where it all began. This is the centermost point of it all.” We are all at the center of it all. Actually, we don’t know that for sure; we can’t prove it mathematically. Scientists just assume that we can’t really be the center of the universe—think what that would imply—but that the phenomenon must be the same for all observers in all places. Still, we don’t actually know.

For us, the universe goes only as far as light has traveled in the billions of years since the universe was formed. This visible universe—the universe we know and can talk about—is a million million million million (that’s 1,000,000,000,000,000,000,000,000) miles across. But according to most theories the universe at large—the meta-universe, as it is sometimes called—is vastly roomier still. According to Rees, the number of light-years to the edge of this larger, unseen universe would be written not “with ten zeroes, not even with a hundred, but with millions.” In short, there’s more space than you can imagine already without going to the trouble of trying to envision some additional beyond.

For a long time the Big Bang theory had one gaping hole that troubled a lot of people—namely that it couldn’t begin to explain how we got here. Although 98 percent of all the matter that exists was created with the Big Bang, that matter consisted exclusively of light gases: the helium, hydrogen, and lithium that we mentioned earlier. Not one particle of the heavy stuff so vital to our own being—carbon, nitrogen, oxygen, and all the rest—emerged from the gaseous brew of creation. But—and here’s the troubling point—to forge these heavy elements, you need the kind of heat and energy of a Big Bang. Yet there has been only one Big Bang and it didn’t produce them. So where did they come from?

Interestingly, the man who found the answer to that question was a cosmologist who heartily despised the Big Bang as a theory and coined the term “Big Bang” sarcastically, as a way of mocking it. We’ll get to him shortly, but before we turn to the question of how we got here, it might be worth taking a few minutes to consider just where exactly “here” is.

2 Welcome To The Solar System

ASTRONOMERS THESE DAYS can do the most amazing things. If someone struck a match on the Moon, they could spot the flare. From the tiniest throbs and wobbles of distant stars they can infer the size and character and even potential habitability of planets much too remote to be seen—planets so distant that it would take us half a million years in a spaceship to get there. With their radio telescopes they can capture wisps of radiation so preposterously faint that the total amount of energy collected from outside the solar system by all of them together since collecting began (in 1951) is “less than the energy of a single snowflake striking the ground,” in the words of Carl Sagan.

In short, there isn’t a great deal that goes on in the universe that astronomers can’t find when they have a mind to. Which is why it is all the more remarkable to reflect that until 1978 no one had ever noticed that Pluto has a moon. In the summer of that year, a young astronomer named James Christy at the U.S. Naval Observatory in Flagstaff, Arizona, was making a routine examination of photographic images of Pluto when he saw that there was something there—something blurry and uncertain but definitely other than Pluto. Consulting a colleague named Robert Harrington, he concluded that what he was looking at was a moon. And it wasn’t just any moon. Relative to the planet, it was the biggest moon in the solar system.

This was actually something of a blow to Pluto’s status as a planet, which had never been terribly robust anyway. Since previously the space occupied by the moon and the space occupied by Pluto were thought to be one and the same, it meant that Pluto was much smaller than anyone had supposed—smaller even than Mercury. Indeed, seven moons in the solar system, including our own, are larger.

Now a natural question is why it took so long for anyone to find a moon in our own solar system. The answer is that it is partly a matter of where astronomers point their instruments and partly a matter of what their instruments are designed to detect, and partly it’s just Pluto. Mostly it’s where they point their instruments. In the words of the astronomer Clark Chapman: “Most people think that astronomers get out at night in observatories and scan the skies. That’s not true. Almost all the telescopes we have in the world are designed to peer at very tiny little pieces of the sky way off in the distance to see a quasar or hunt for black holes or look at a distant galaxy. The only real network of telescopes that scans the skies has been designed and built by the military.”

We have been spoiled by artists’ renderings into imagining a clarity of resolution that doesn’t exist in actual astronomy. Pluto in Christy’s photograph is faint and fuzzy—a piece of cosmic lint—and its moon is not the romantically backlit, crisply delineated companion orb you would get in a National Geographic painting, but rather just a tiny and extremely indistinct hint of additional fuzziness. Such was the fuzziness, in fact, that it took seven years for anyone to spot the moon again and thus independently confirm its existence.

One nice touch about Christy’s discovery was that it happened in Flagstaff, for it was there in 1930 that Pluto had been found in the first place. That seminal event in astronomy was largely to the credit of the astronomer Percival Lowell. Lowell, who came from one of the oldest and wealthiest Boston families (the one in the famous ditty about Boston being the home of the bean and the cod, where Lowells spoke only to Cabots, while Cabots spoke only to God), endowed the famous observatory that bears his name, but is most indelibly remembered for his belief that Mars was covered with canals built by industrious Martians for purposes of conveying water from polar regions to the dry but productive lands nearer the equator.

Lowell’s other abiding conviction was that there existed, somewhere out beyond Neptune, an undiscovered ninth planet, dubbed Planet X. Lowell based this belief on irregularities he detected in the orbits of Uranus and Neptune, and devoted the last years of his life to trying to find the gassy giant he was certain was out there. Unfortunately, he died suddenly in 1916, at least partly exhausted by his quest, and the search fell into abeyance while Lowell’s heirs squabbled over his estate. However, in 1929, partly as a way of deflecting attention away from the Mars canal saga (which by now had become a serious embarrassment), the Lowell Observatory directors decided to resume the search and to that end hired a young man from Kansas named Clyde Tombaugh.

Tombaugh had no formal training as an astronomer, but he was diligent and he was astute, and after a year’s patient searching he somehow spotted Pluto, a faint point of light in a glittery firmament. It was a miraculous find, and what made it all the more striking was that the observations on which Lowell had predicted the existence of a planet beyond Neptune proved to be comprehensively erroneous. Tombaugh could see at once that the new planet was nothing like the massive gasball Lowell had postulated, but any reservations he or anyone else had about the character of the new planet were soon swept aside in the delirium that attended almost any big news story in that easily excited age. This was the first American-discovered planet, and no one was going to be distracted by the thought that it was really just a distant icy dot. It was named Pluto at least partly because the first two letters made a monogram from Lowell’s initials. Lowell was posthumously hailed everywhere as a genius of the first order, and Tombaugh was largely forgotten, except among planetary astronomers, who tend to revere him.

A few astronomers continue to think there may be a Planet X out there—a real whopper, perhaps as much as ten times the size of Jupiter, but so far out as to be invisible to us. (It would receive so little sunlight that it would have almost none to reflect.) The idea is that it wouldn’t be a conventional planet like Jupiter or Saturn—it’s much too far away for that; we’re talking perhaps 4.5 trillion miles—but more like a sun that never quite made it. Most star systems in the cosmos are binary (double-starred), which makes our solitary sun a slight oddity.

As for Pluto itself, nobody is quite sure how big it is, or what it is made of, what kind of atmosphere it has, or even what it really is. A lot of astronomers believe it isn’t a planet at all, but merely the largest object so far found in a zone of galactic debris known as the Kuiper belt. The Kuiper belt was actually theorized by an astronomer named F. C. Leonard in 1930, but the name honors Gerard Kuiper, a Dutch native working in America, who expanded the idea. The Kuiper belt is the source of what are known as short-period comets—those that come past pretty regularly—of which the most famous is Halley’s comet. The more reclusive long-period comets (among them the recent visitors Hale-Bopp and Hyakutake) come from the much more distant Oort cloud, about which more presently.

It is certainly true that Pluto doesn’t act much like the other planets. Not only is it runty and obscure, but it is so variable in its motions that no one can tell you exactly where Pluto will be a century hence. Whereas the other planets orbit on more or less the same plane, Pluto’s orbital path is tipped (as it were) out of alignment at an angle of seventeen degrees, like the brim of a hat tilted rakishly on someone’s head. Its orbit is so irregular that for substantial periods on each of its lonely circuits around the Sun it is closer to us than Neptune is. For most of the 1980s and 1990s, Neptune was in fact the solar system’s most far-flung planet. Only on February 11, 1999, did Pluto return to the outside lane, there to remain for the next 228 years.

So if Pluto really is a planet, it is certainly an odd one. It is very tiny: just one-quarter of 1 percent as massive as Earth. If you set it down on top of the United States, it would cover not quite half the lower forty-eight states. This alone makes it extremely anomalous; it means that our planetary system consists of four rocky inner planets, four gassy outer giants, and a tiny, solitary iceball. Moreover, there is every reason to suppose that we may soon begin to find other even larger icy spheres in the same portion of space. Then we will have problems. After Christy spotted Pluto’s moon, astronomers began to regard that section of the cosmos more attentively and as of early December 2002 had found over six hundred additional Trans-Neptunian Objects, or Plutinos as they are alternatively called. One, dubbed Varuna, is nearly as big as Pluto’s moon. Astronomers now think there may be billions of these objects. The difficulty is that many of them are awfully dark. Typically they have an albedo, or reflectiveness, of just 4 percent, about the same as a lump of charcoal—and of course these lumps of charcoal are about four billion miles away.

And how far is that exactly? It’s almost beyond imagining. Space, you see, is just enormous—just enormous. Let’s imagine, for purposes of edification and entertainment, that we are about to go on a journey by rocketship. We won’t go terribly far—just to the edge of our own solar system—but we need to get a fix on how big a place space is and what a small part of it we occupy.

Now the bad news, I’m afraid, is that we won’t be home for supper. Even at the speed of light, it would take seven hours to get to Pluto. But of course we can’t travel at anything like that speed. We’ll have to go at the speed of a spaceship, and these are rather more lumbering. The best speeds yet achieved by any human object are those of the Voyager 1 and 2 spacecraft, which are now flying away from us at about thirty-five thousand miles an hour.

The reason the Voyager craft were launched when they were (in August and September 1977) was that Jupiter, Saturn, Uranus, and Neptune were aligned in a way that happens only once every 175 years. This enabled the two Voyagers to use a “gravity assist” technique in which the craft were successively flung from one gassy giant to the next in a kind of cosmic version of “crack the whip.” Even so, it took them nine years to reach Uranus and a dozen to cross the orbit of Pluto. The good news is that if we wait until January 2006 (which is when NASA’s New Horizons spacecraft is tentatively scheduled to depart for Pluto) we can take advantage of favorable Jovian positioning, plus some advances in technology, and get there in only a decade or so—though getting home again will take rather longer, I’m afraid. At all events, it’s going to be a long trip.

Now the first thing you are likely to realize is that space is extremely well named and rather dismayingly uneventful. Our solar system may be the liveliest thing for trillions of miles, but all the visible stuff in it—the Sun, the planets and their moons, the billion or so tumbling rocks of the asteroid belt, comets, and other miscellaneous drifting detritus—fills less than a trillionth of the available space. You also quickly realize that none of the maps you have ever seen of the solar system were remotely drawn to scale. Most schoolroom charts show the planets coming one after the other at neighborly intervals—the outer giants actually cast shadows over each other in many illustrations—but this is a necessary deceit to get them all on the same piece of paper. Neptune in reality isn’t just a little bit beyond Jupiter, it’s way beyond Jupiter—five times farther from Jupiter than Jupiter is from us, so far out that it receives only 3 percent as much sunlight as Jupiter.

Such are the distances, in fact, that it isn’t possible, in any practical terms, to draw the solar system to scale. Even if you added lots of fold-out pages to your textbooks or used a really long sheet of poster paper, you wouldn’t come close. On a diagram of the solar system to scale, with Earth reduced to about the diameter of a pea, Jupiter would be over a thousand feet away and Pluto would be a mile and a half distant (and about the size of a bacterium, so you wouldn’t be able to see it anyway). On the same scale, Proxima Centauri, our nearest star, would be almost ten thousand miles away. Even if you shrank down everything so that Jupiter was as small as the period at the end of this sentence, and Pluto was no bigger than a molecule, Pluto would still be over thirty-five feet away.

So the solar system is really quite enormous. By the time we reach Pluto, we have come so far that the Sun—our dear, warm, skin-tanning, life-giving Sun—has shrunk to the size of a pinhead. It is little more than a bright star. In such a lonely void you can begin to understand how even the most significant objects—Pluto’s moon, for example—have escaped attention. In this respect, Pluto has hardly been alone. Until the Voyager expeditions, Neptune was thought to have two moons; Voyager found six more. When I was a boy, the solar system was thought to contain thirty moons. The total now is “at least ninety,” about a third of which have been found in just the last ten years.

The point to remember, of course, is that when considering the universe at large we don’t actually know what is in our own solar system.

Now the other thing you will notice as we speed past Pluto is that we are speeding past Pluto. If you check your itinerary, you will see that this is a trip to the edge of our solar system, and I’m afraid we’re not there yet. Pluto may be the last object marked on schoolroom charts, but the system doesn’t end there. In fact, it isn’t even close to ending there. We won’t get to the solar system’s edge until we have passed through the Oort cloud, a vast celestial realm of drifting comets, and we won’t reach the Oort cloud for another—I’m so sorry about this—ten thousand years. Far from marking the outer edge of the solar system, as those schoolroom maps so cavalierly imply, Pluto is barely one-fifty-thousandth of the way.

Of course we have no prospect of such a journey. A trip of 240,000 miles to the Moon still represents a very big undertaking for us. A manned mission to Mars, called for by the first President Bush in a moment of passing giddiness, was quietly dropped when someone worked out that it would cost $450 billion and probably result in the deaths of all the crew (their DNA torn to tatters by high-energy solar particles from which they could not be shielded).

Based on what we know now and can reasonably imagine, there is absolutely no prospect that any human being will ever visit the edge of our own solar system—ever. It is just too far. As it is, even with the Hubble telescope, we can’t see even into the Oort cloud, so we don’t actually know that it is there. Its existence is probable but entirely hypothetical.*2

About all that can be said with confidence about the Oort cloud is that it starts somewhere beyond Pluto and stretches some two light-years out into the cosmos. The basic unit of measure in the solar system is the Astronomical Unit, or AU, representing the distance from the Sun to the Earth. Pluto is about forty AUs from us, the heart of the Oort cloud about fifty thousand. In a word, it is remote.

But let’s pretend again that we have made it to the Oort cloud. The first thing you might notice is how very peaceful it is out here. We’re a long way from anywhere now—so far from our own Sun that it’s not even the brightest star in the sky. It is a remarkable thought that that distant tiny twinkle has enough gravity to hold all these comets in orbit. It’s not a very strong bond, so the comets drift in a stately manner, moving at only about 220 miles an hour. From time to time some of these lonely comets are nudged out of their normal orbit by some slight gravitational perturbation—a passing star perhaps. Sometimes they are ejected into the emptiness of space, never to be seen again, but sometimes they fall into a long orbit around the Sun. About three or four of these a year, known as long-period comets, pass through the inner solar system. Just occasionally these stray visitors smack into something solid, like Earth. That’s why we’ve come out here now—because the comet we have come to see has just begun a long fall toward the center of the solar system. It is headed for, of all places, Manson, Iowa. It is going to take a long time to get there—three or four million years at least—so we’ll leave it for now, and return to it much later in the story.